August 11, 2000

     Meteors

Frequently, meteors light up the night sky by the hundreds for several nights around this time of year.  The bright streaks give them the nickname "shooting stars."

Meteors are rock particles, most no bigger than grains of beach sand.  They are probably made up of silicates and other stony materials, plus iron and nickel in metallic flakes.  As they move toward the Earth, they hit the fringes of the atmosphere, about 60 miles above us and burn, so what we see are short-lived streaks of light.

Several times each year, meteors can be seen with much greater than average frequency -- a meteor shower.  Showers occur when the Earth encounters swarms of particles moving together through space.  Some of these particles are debris from a comet last seen during the Civil War.

Comets travel in wide-looping orbits around the Sun.  As they disintegrate, they drop sandy pebbles in their wake.  The Swift-Tuttle comet, which last passed near Earth in 1862, has done more than its share of littering in space over the centuries.  Since the Earth circles the sun once a year, our planet passes through the path of debris left by Swift-Tuttle every August.  The meteors tend to come from the general direction of the constellation Perseus, hence the name Perseid meteor shower for this annual August display.

There are several meteor showers at various times of the year but the best is the Perseid shower.  Without bright moonlight, meteors can be seen with a frequency of about one per minute during a typical Perseid shower.